City planner Jeff Speck in his book Walkable Cities: How Downtown Can Save America, One Step at a Time makes clear the point that in the United States the air pollution dynamic has shifted. Rather than the bulk of America’s smog-forming pollution coming from industry, it is now sourced mainly from vehicle exhaust.1
How this happened all has to do with the city dynamic, whereby housing, business and industry were by-and-large grouped together in the central core and characteristic of late 19th century practice, transitioning to a building paradigm all based on the automobile, highways and one that embraced more and